Sensor unit for automatically switching of lighting devices and coupling medium for a sensor unit

ABSTRACT

A sensor unit for automatic switching of lighting devices of motor vehicles is described. The sensor unit includes at least one light-sensitive sensor, a filter element being situated upstream from it, and the filter element filtering out infrared light. A coupling medium for improving the switching points of the sensor unit and the use of a coupling medium and a filter for improving the switching points of the sensor unit are also described.

FIELD OF THE INVENTION

The present invention relates to a sensor unit for automatic switchingof lighting devices, a coupling medium for coupling such a sensor unitto a pane, as well as the utilization of a coupling medium and a filter.

BACKGROUND INFORMATION

Numerous such sensor units with which the lighting devices of a motorvehicle are controlled as a function of signals from light-sensitivesensors are known, e.g., from published German Patent Application 199 33642. They have sensors which detect the lighting conditions outside thevehicle, the sensors being connected to an analyzing device in which itis determined from the sensor signals whether the currently existinglighting conditions make a change in the switching state of the lightingdevices necessary. The lighting devices are then switched on or offaccording to this analysis.

SUMMARY OF THE INVENTION

The sensor unit according to an embodiment of the present invention hasthe advantage over the related art that the switching characteristics,in particular individual on and off switching points of the sensor unit,are substantially improved by the upstream placement of a filter elementwhich filters infrared light out.

In an embodiment of the present invention, the filter element filtersout light having wavelengths of more than 750 nm, since these are abovethe perception threshold of the human eye.

In another embodiment, the filter element has adhesive properties,since, in this way, the filter element may be directly glued to theinside or outside of the windshield of the motor vehicle.

In an additional embodiment, the filter element is provided with lensproperties, thus combining the filter property with the lens property.

Furthermore, in another embodiment, several sensors, which detect lightfrom different directions, are provided. In this case, differentfiltering thresholds of the filter elements may also be provided for thedifferent directions.

In another embodiment, an optical light guide, attachable to a pane viaa coupling medium, is placed upstream from the sensor and the pane orthe coupling element and filters out the infrared light havingwavelengths of more than 750 nm in particular. Regular sensor units maythus be retrofitted with an infrared filter layer.

The coupling medium according to an embodiment of the present inventionhas an infrared filter for the sensor unit placed upstream from thetransmitter such that, for example, the response of an existing sensorunit may be improved by simply replacing the coupling medium.

The coupling medium may be composed of a sheet or a film having anadhesive applied to it, since the coupling medium may thus be able tohold the sensor unit on the pane in a self-adhesive manner.

In an additional embodiment, the coupling medium has an overallcurvature, since gas bubbles or air bubbles in the coupling area causeinterfering diffusions which may easily be prevented in this way. Ofcourse, the sensor unit may also have a slight curvature on its mountingside, causing the same effect.

In other embodiments, an optically transparent coupling medium or afilter for filtering radiation is used for automatic control of lightingdevices.

In yet another embodiment, the sensor unit has a control device forcontrolling the lighting devices, the control device changing the on andoff switching points of the lighting devices by taking into account theIR signals measured separately. Since IR signals are available in manycases from the climate control or from a rain sensor, the switchingcharacteristics of the sensor unit may thus be improved withoutincurring any additional costs.

In another embodiment of the present invention, values are assigned tothe signals of the light sensors and to the IR signals, respectively,and the values of the former signals are acted upon by the values of theIR signals. A factor is considered here, resulting in an electronicfilter effect.

In another embodiment, the switching thresholds of the control deviceare raised or lowered taking the IR signals into account.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a sensor unit according to thepresent invention.

FIG. 2 shows a radiation spectrum of electromagnetic radiation.

FIG. 3 shows an exemplary signal characteristic of the sensors.

DETAILED DESCRIPTION

FIG. 1 schematically shows an embodiment of a sensor unit 10 accordingto the present invention.

Sensor unit 10 is essentially composed of a control device 12, which isable to control lighting devices 14, and sensors 16 which are connectedto control device 12, emitting signals (S) to control device 12.Standard receivers BPW 24S of Infineon Corporation may be used assensors, for example.

Furthermore, an optical light guide 18 having imaging structures 19which are designed as lenses or holograms is placed upstream fromsensors 16. Sensors 16 are positioned approximately on the optical axisof structures 19 and are supported by a mutual circuit board 20 on whichcontrol device 12 is also situated. Of course, structure 19 is notnecessary for detecting the overall surrounding light; however, a lensehaving an extremely long focal distance f, up to an infinite focaldistance, may be used, for example.

Sensor unit 10 is attached to a pane 24, the windshield of a motorvehicle, for example, via a coupling medium 22. Coupling medium 22 issituated between optical light guide 18 and pane 24. Normally, thehousing of sensor unit 10 is sealed by optical light guide 18.

An IR film 26, reflecting the infrared radiation having a wave length ofmore than 700 nm, is situated in pane 24. In this way, very little or noincident infrared radiation is transmitted in the direction of sensors16.

Of course, an IR film may also be placed in coupling medium 22 or on itssurfaces. It is also possible in particular to design coupling medium 22of a material which is relatively non-transparent to infrared radiation.

Optical light guide 18 may be made of a material which isnon-transparent to infrared light, or at least the areas of opticallight guide 18 which focus the incident radiation on sensors 16 may bemade non-transparent to infrared light. For example, appropriate filtermolecules may be added during injection molding or a multi-componentinjection molding method may be used.

Applying infrared filters directly on sensors 16 or immediately upstreamof the same represents another alternative. In particular, infraredinsensitive sensors 16 may also be used.

It is also conceivable to apply an infrared-transparent layer on opticallight guide 18.

In another embodiment of the present invention, an infrared-transparentfilm may be glued onto pane 24 in the area of sensor unit 10, or it maybe attached in a different manner, e.g., by adhesion.

Of course, the features of different embodiments explained in thepreceding paragraphs may be combined in many different ways.

The IR threshold may be accurately adjusted by the selection of suitablematerials, their configurations, and transmission spectra.

Furthermore, sensor unit 10 may be integrated into a rain sensor.Infrared-blocking layers (sun protect layers) are typically recessed inpane 24 in the area of the rain sensor, since numerous rain sensors useinfrared light for detecting precipitation. The infrared-blocking layermay again be inserted in the area of sensor unit 10 as a window,or—depending on the geometry of the rain sensor—the rain sensorincluding the sensor unit may be situated in the edge area of theinfrared-blocking layer.

In a further variant embodiment, coupling medium 22 may have aninfrared-blocking design in the area of the sensor unit and may betransparent to infrared light in the areas of the rain sensor. Couplingmedium 22 may be manufactured by a two-component or multi-componentinjection molding method.

FIG. 2 shows a radiation diagram of electromagnetic radiation. Thevisible radiation, i.e., the light radiation, ranges approximately from400 nm to 750 nm wavelength. The infrared radiation extendsapproximately between 750 nm and 0.1 mm wavelength. In addition tovisible radiation, sunlight also has numerous other components, such as,for example, a large portion of infrared radiation.

In another embodiment of the present invention, the effects of theinfrared radiation may be compensated electronically. IR signals IRS aresupplied to control device 12 for this purpose. In the control device,values are assigned to IR signals IRS and to signals S of sensors 16. Anoffset is calculated by multiplying the values of IR signals IRS by afactor F and adding to the values assigned to signals S.

A signal characteristic thus obtained is illustrated in FIG. 3. Signal Sand the corrected signal over time are shown as examples here. IR signalIRS is constant in the period shown; it changes over a longer period oftime, of course.

Other algorithms for taking the IR signals into account are possible.For example, switching thresholds or other parameters that arecharacteristic for the on and off switching points of control device 12may be changed by taking the IR signals into account.

IR signals IRS may be generated by using a specific receiver, e.g., aBPW 34 photodiode having a daylight blocking filter made by the InfineonCorporation. This receiver emits IR signals IRS which are a measure ofthe incident infrared radiation. However, such a photodiode or a similarphotodiode is frequently already integrated into rain sensors so thatsuitable IR signals IRS are already available.

It is also possible to separately measure the ambient luminosity indifferent spectral ranges, e.g., infrared, red, green, blue,ultraviolet, and in different spatial directions. The different measuredvalues may then be separately weighted and better adapted to the humanperception threshold. This makes it possible to optimally adjust the onand off switching points to the vehicle driver. The weighting factorsmay be readjusted by the vehicle driver himself, in order to adjust thesensitivity of the sensor unit to his or her individual needs. Such anadjustment may take place, for example, via central electronics, i.e.,for example, via a touch screen of a driver interface which, forexample, also has a climate control, a navigation system, and othercomponents known in this connection to those skilled in the art.

1. A sensor unit for automatically switching a lighting device of amotor vehicle, comprising: at least one light-sensitive sensor, thesensor detecting a brightness in light surrounding the sensor unit; acontrol device configured to control the lighting device in accordancewith the detected brightness; and an arrangement for compensating for aneffect from infrared light; wherein the arrangement includes a filterelement situated upstream from the sensor, the filter element filteringout infrared light; and wherein the filter element is substantiallytransparent to all visible light.
 2. The sensor unit as recited in claim1, wherein the filter element filters out light having wavelengths ofmore than 750 nanometers.
 3. The sensor unit as recited in claim 1,wherein the arrangement has an adhesive property.
 4. The sensor unit asrecited in claim 1, wherein the arrangement has lens properties.
 5. Thesensor unit as recited in claim 1, wherein a plurality oflight-sensitive sensors are provided.
 6. The sensor unit as recited inclaim 1, wherein the arrangement includes an optical light guide,situated upstream from the sensor, and a coupling medium, the opticallight guide being attachable by the coupling medium to a pane, whereinone of the pane and the coupling medium filters out infrared lighthaving wavelengths of more than 750 nanometers.
 7. A sensor unit forautomatically switching a lighting device of a motor vehicle,comprising: at least one light-sensitive sensor, the sensor detecting abrightness in light surrounding the sensor unit; an arrangement forcompensating for an effect from infrared light; and a control device,wherein the control device controls the lighting device, the controldevice receiving IR signals from the light-sensitive sensor, the IRsignals representing a measure of the infrared light measured by thelight-sensitive sensor, and the control device analyzing light signalsfrom the light-sensitive sensor, taking the IR signals into account tocontrol the lighting device.
 8. A sensor unit for automaticallyswitching a lighting device of a motor vehicle, comprising: at least onelight-sensitive sensor, the sensor detecting a brightness in lightsurrounding the sensor unit; an arrangement for compensating for aneffect from infrared light; and a control device, wherein the controldevice controls the lighting device, the control device receiving IRsignals from the light-sensitive sensor, the IR signals representing ameasure of the infrared light measured by the light-sensitive sensor,and the control device analyzing light signals from the light-sensitivesensor, taking the IR signals into account, wherein values are assignedto the light signals and to the IR signals, the values of the IR signalsbeing superimposed upon the values of the light signals, taking apredetermined factor into account.
 9. A sensor unit for automaticallyswitching a lighting device of a motor vehicle, comprising: at least onelight-sensitive sensor, the sensor detecting a brightness in lightsurrounding the sensor unit; an arrangement for compensating for aneffect from infrared light; and a control device, wherein the controldevice controls the lighting device, the control device receiving IRsignals from the light-sensitive sensor, the IR signals representing ameasure of the infrared light measured by the light-sensitive sensor,and the control device analyzing light signals from the light-sensitivesensor, taking the IR signals into account, wherein the control devicehas at least one switching threshold that is changeable by taking the IRsignals into account.